Magnetoresistance effect device having hard magnetic film structural body

ABSTRACT

A base film of a hard magnetic film containing Co as a structural element has a crystal metal base film such as a Cr film formed on the main surface of a substrate and a reactive base film (mixing layer) formed between the substrate and the crystal metal base film and having a reactive amorphous layer containing a structural element of the substrate and a structural element of the crystal metal base film. A hard magnetic film containing Co as a structural element is formed on the crystal metal base film. With the crystal metal base film such as the Cr film formed on an amorphous layer, a hard magnetic film with a bi-crystal structure can be obtained with high reproducibility. With the hard magnetic film, magnetic characteristics such as coercive force Hc, residual magnetization Mr, saturated magnetization Ms, and square ratio S can be improved without need to use a thick base film. The hard magnetic film containing Co as a structural element is applied to a bias magnetic field applying film of a magnetoresistance effect device and a record layer of a magnetic record medium.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a hard magnetic film structural body, amagnetoresistance effect device thereof, a magnetic head thereof, amagnetic recording/reproducing head thereof, a magnetic record mediumthereof, and magnetic storing apparatus thereof.

2. Description of the Related Art

In magnetic recording apparatuses such as HDDs, record track widthsthereof have been decreased so as to increase record densities. Tocompensate the decrease of the reproduced output due to the decrease ofthe record track widths, magnetic heads having high sensitivemagnetoresistance effect devices (MR devices) have been used. Theseheads are referred to as MR heads. In particular, MR heads having spinvalve films are hopeful successors in the next generation. The spinvalve film is composed of a multi-layer magnetic film of which a firstferromagnetic film, a non-magnetic film, a second ferromagnetic film,and an anti-ferromagnetic film layered in the order. The magnetizationof the first ferromagnetic film rotates corresponding to a signalmagnetic field (hereinafter, the first ferromagnetic film is referred toas a magnetic sensible layer). The magnetization of the secondferromagnetic film is fixed by a bias magnetic field of theanti-ferromagnetic film. Hereinafter, the second ferromagnetic film isreferred to a fixed magnetization layer. The spin valve film has a giantmagnetoresistance effect (GMR).

In an MR head having a spin valve film, Barkhausen noise due to amagnetic domain wall on the magnetic sensible layer is becoming apractically serious problem to be solved. In other words, when anexternal magnetic field is applied to a magnetic sensible layer having avariety of magnetic domains rather than a controlled magnetic domain,the magnetic directions of the individual magnetic domains are arrangedto one direction at a time. At this point, a noise (Barkhausen noise)takes place in the output waveform. To remove the Barkhausen noise, aso-called abutted junction type MR head of which a hard magnetic film 2such as a CoPt film is disposed on both sides of a spin valve film 1 asshown in FIG. 36 has been proposed. The magnetic domains of the magneticsensible layer are controlled by a bias magnetic field (vertical bias)of the hard magnetic films 2 disposed on both sides of the magneticsensible layer. When a variety of magnetic domains of the magneticsensible layer are controlled to a single magnetic domain with such abias magnetic field, the Barkhausen noise can be suppressed.

In the MR head shown in FIG. 36, a pair of electrodes 3 that supply asense current are formed on the spin valve film 1. The spin valve film 1is sandwiched by a pair of upper and lower magnetic shield layers 6 and7 disposed through magnetic gap films 4 and 5, respectively. Thus, ashield type MR head is structured.

In this case, the hard magnetic film 2 preferably has a stably largecoercive force Hc so as to stably maintain the magnetic domain controlof the magnetic sensible layer for a long time. In addition, the hardmagnetic film 2 preferably has a large residual magnetization Mr so asto properly apply a bias magnetic field to various magnetic sensiblelayers. However, in conventional MR heads, the film thickness of thehard magnetic film cannot be sufficiently increased due to a structuralreason. In addition, the crystal structure of the hard magnetic filmcannot be sufficiently controlled. Thus, the coercive force Hc and theresidual magnetization Mr of the hard magnetic film are insufficient.

Moreover, as the densities of the magnetic recording apparatusesincrease, the floating distance of the MR head from the magnetic recordmedium tends to decrease. In reality, it is predicted that the MR headis used in a low floating state, a pseudo-contacting state, and finallya contacting state. When the distance between the MR head and the recordmedium decreases, a magnetization reversal tends to take place in a hardmagnetic field with a low coercive force. When the magnetizationreversal takes place in the hard magnetic film, the magnetization of themagnetic sensible layer becomes unstable, thereby forming magneticdomains. As described above, the magnetic domains formed on the magneticsensible layers result in the Barkhausen noise.

As countermeasures for increasing the coercive force of a hard magneticfilm, the crystal characteristics thereof is improved with a very thicknon-magnetic base film with a film thickness of for example 100 nm ormore for increasing the effect of the base film (seed layer). Theimprovement of the crystal characteristics of the hard magnetic filmcontributes to the increase of the magnetic anisotropy. Thus, thecoercive force of the hard magnetic film can be increased. Suchcountermeasures can be applied to a hard magnetic film as a magneticrecord layer of a magnetic record medium.

However, in the abutted junction type MR head, when the magnetic gapnarrows for a high density, a bias magnetic field leaks to a magneticshield layer, thereby decreasing the effective bias magnetic fieldapplied to a magnetic sensible layer. In addition, when a thicknon-magnetic base film is used, in the abutted junction type, since thethick non-magnetic base film is disposed between a hard magnetic filmand a spin valve film, the bias effect against the magnetic sensiblelayer decreases.

As countermeasures for improving the coercive force of a hard magneticfilm, the film thickness thereof may be increased so as to compensatethe bias magnetic field. However, in the magnetic head having a narrowtrack for high density recording, the increase of film thickness of thehard magnetic film results in the decrease of sensitivity. When a hardmagnetic film that is thicker than a spin valve is used, the centerportion of the film thickness of the hard magnetic film becomes close toa fixed magnetization layer. Since an anisotropic magnetic field of ananti-ferromagnetic film that fixes the magnetization of the fixedmagnetization layer is weak, the magnetization reversal of the fixedmagnetization layer tends to take place in the vicinity of the interfacebetween the hard magnetic film and the anti-ferromagnetic film. Themagnetization reversal of the fixed magnetization layer results in anoise.

Instead of the above-described abutted junction type, for example asshown in FIG. 37, a bias type of which a spin valve film 1 spreads on ahard magnetic film 3 and thereby a magnetic sensible layer of the spinvalve film 1 and the hard magnetic film 2 are exchange-coupling has beenproposed. In such a head structure (overlaid structure), after a thickhard magnetic film 2 is etched by for example ion milling process, aspin valve film 1 is formed. Thus, the surface of the lower magnetic gapfilm 4 that has been etched becomes rough.

When the spin valve film 1 is formed on the lower magnetic gap film 4that is not flat, magnetic characteristics become unstable such that theanisotropic magnetic field Hk becomes unstable, the coercive force Hctakes place in the direction of difficult axis, and the inter-layercoupling magnetic field Hin between the magnetic sensible layer and thefixed magnetization layer increases. Such an instability of the magneticcharacteristics results in the Barkhausen noise. The surface roughnessof the lower magnetic gap film 4 also takes place when the surfaceroughness of the hard magnetic film 2 is transferred by the ion millingprocess.

In addition, as shown in FIG. 38, even if the coercive force Hc (Mpoint) of the hard magnetic film (in the overlaid structure) is large,when the residual magnetization Mr is low, the total coercive force Hc(L point) of the GMR film (such as a spin valve film) and the hardmagnetic film decreases, thereby increasing the occurrence of theBarkhausen noise. In the hard magnetic film of conventional the MR head,the sufficient residual magnetization Mr has not been obtained.

As described above, in the MR head having the spin valve film, it isstrongly desired to improve magnetic characteristics such as thecoercive force Hc, residual magnetization Mr, saturated magnetizationMs, and square ratio S of the hard magnetic film without need to use athick non-magnetic base film. As with the MR head having the spin valvefilm, in an MR head having a magnetoresistance effect film (AMR film)with the anisotropic magnetoresistance effect (AMR), a hard magneticfilm is used to apply a horizontal bias. In this AMR head, likewise, itis desired to improve magnetic characteristics such as the coerciveforce Hc, residual magnetization Mr, saturated magnetization Ms, andsquare ration S of the hard magnetic film.

Furthermore, a magnetic storing apparatus such as a magnetoresistanceeffect random access memory (MRAM) having a spin valve film has beenstudied. In this case, a satisfactory bias magnetic field is required.

On the other hand, in the hard magnetic film as the magnetic recordlayer of the magnetic record medium, to accomplish a low noise in highdensity magnetic recording, the value of [Mr·t (residual magnetizationMr×film thickness t)] should be small. However, in the Co type hardmagnetic film, when the film thickness thereof is 10 nm or less, goodmagnetic characteristics cannot be obtained. In reality, the coerciveforce Hc, the square ratio S, and so forth are degraded. For example,when the film thickness t of the Co type hard magnetic film is decreasedso as to decrease the value of (Mr·t), the crystal characteristics aredegraded. In this case, the anisotropic magnetic field Hk^(grain) of thecrystal grains degrades, thereby decreasing the coercive force Hc.

To accomplish the above-described low floating state, pseudo-contactingstate, and contacting state of the magnetic head, the surface flatnessof the magnetic record medium should be improved. To improve the surfaceflatness of the hard magnetic film as the magnetic record layer, thefilm thickness of the hard magnetic film including the film thickness ofthe base film should be decreased. Generally, when the film thickness ofthe base film is large, the diameters of crystal grains often increase.When the diameters of crystal grains become large as the film thicknessincreases, the boundary of crystal grains of the film surface becomesrough. Further, even if the boundary of crystal grains does not increaseas the film thickness increases, crystal grains become column-like andthe surface roughness of the film is large when the film thickness islarge. (In any case,) when the film thickness of the base film is large,the diameters of crystal grains become large.

However, as described above, to improve the crystal characteristics ofthe Co type hard magnetic film, a base film as thick as 100 nm isrequired. This is because when the thickness of the base film is small,the crystal structure of the Co type hard magnetic film having a hcpstructure cannot be satisfactorily controlled. In reality, the axis c ofthe Co type hard magnetic material cannot be oriented to the surfacethereof.

The film thickness of the base film of the Co type hard magnetic filmshould be decreased so as to accomplish high density recording. Asdescribed above, when the film thickness of the base film is large, thediameters of crystal grains of the Co type hard magnetic film becomelarge. Thus, the number of magnetic grains per unit bit decreases,thereby causing the noise to increase. However, when the film thicknessof the base film is decreased, the effect thereof is degraded. Thus, thebase film cannot provide the Co type hard magnetic film with good hardmagnetic characteristics.

Consequently, in the hard magnetic film as a magnetic record layer of amagnetic record medium, even if the film thickness of the hard magneticfilm is small, without need to use a thick base film, it is stronglyrequired to improve characteristics such as the coercive force Hc,residual magnetization Mr, saturated magnetization Ms, square ratio S,and so forth.

On the other hand, in the field of the magnetic record mediums, asurface magnetic record medium having a hard magnetic film with abi-crystal structure has been expected as a low noise medium. Thebi-crystal structure represents that sub-grains are present in eachmain-grain. In a main-grain, the surface components of the axis c of thesub-grains are perpendicular to each other. Since sub-grains function asmagnetic grains, a low noise can be accomplished. In addition, a largecoercive force can be obtained.

However, in the bi-crystal structure, a good fabrication conditionthereof has not been established. It is said that the base film shouldhave a bcc (body-centered cubic) (200) orientation. In the bccstructure, normally a plane (110) is the densest plane. Thus, on a basefilm that is simply formed, the bi-crystal structure cannot be obtained.Conventionally, the substrate should be heated at a temperature of atleast 200° C. when the film is formed. However, even in such a process,the bi-crystal structure cannot be obtained with high reproducibility.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide a hardmagnetic film structural body having a hard magnetic film with excellentmagnetic characteristics such as coercive force Hc, residualmagnetization Mr, saturated magnetization Ms, and square ratio S, thehard magnetic film being obtained with high reproducibility without needto use a thick base film. Another object of the present invention is toprovide a hard magnetic film structural body having a hard magnetic filmwith a bi-crystal structure, the hard magnetic film being obtained withhigh reproducibility. A further object of the present invention is toprovide a magnetoresistance effect device having a hard magnetic filmwith the above-described excellent magnetic characteristics, a magnetichead thereof, a magnetic recording/reproducing head thereof, a magneticrecord medium thereof, and a magnetic storing apparatus thereof.

A first aspect of the present invention is a hard magnetic filmstructural body, comprising a substrate having a main surface, a crystalmetal base film formed on the main surface of said substrate, anamorphous layer formed between said substrate and said crystal metalbase film, and a hard magnetic film formed on said crystal metal basefilm and containing Co as a structural element, said hard magnetic filmhaving a bi-crystal structure.

A second aspect of the present invention is a hard magnetic filmstructural body comprising a substrate having a main surface, a crystalmetal base film formed on the main surface of said substrate, a mixinglayer formed between said substrate and said crystal metal base film andcontaining structural elements of said substrate and structural elementsof said crystal metal base film, and a hard magnetic film formed on saidcrystal metal base film and containing Co as a structural element, saidhard magnetic film having a bi-crystal structure.

A third aspect of the present invention is a magnetoresistance effectdevice, comprising a substrate having a main surface, amagnetoresistance effect film formed on the main surface of saidsubstrate and having a magnetic field detecting portion, a pair of biasmagnetic field applying films disposed adjacent to both edge portions ofthe magnetic field detecting portion, the bias magnetic field applyingfilms having hard magnetic films containing Co as a structural elementand having a bi-crystal structure.

A fourth aspect of the present invention is a magnetoresistance effectdevice, the magnetoresistance effect device comprising a substratehaving a insulating layer as a surface layer, a magnetoresistance effectfilm formed on the insulating layer of said substrate and having amagnetic field detecting portion, a pair of longitudianl biasing films(a pair of bias magnetic field applying films) disposed adjacent to bothedge portions of the magnetic field detecting portion and having anamorphous layer, a metal crystal layer, and a hard magnetic filmcontaining Co as a structural element successively layered on theinsulating layer of said substrate, and a pair of electrodes forsupplying a current to said magnetoresistance effect film.

A fifth aspect of the present invention is a magnetoresistance effectdevice, comprising a substrate having a main surface, amagnetoresistance effect film formed on the main surface of saidsubstrate and having a magnetic field detecting portion, a pair oflongitudinal biasing films (a pair of bias magnetic field applyingfilms) disposed adjacent to both edge portions of the magnetic fielddetecting portion and having a crystal metal base film on the mainsurface of the substrate, a mixing layer formed between the substrateand the crystal metal base film and containing structural elements ofthe substrate and structural elements of said crystal metal base film,and a hard magnetic film formed on the crystal metal base film andcontaining Co as a structural element, and a pair of electrodes forsupplying a current to said magnetoresistance effect film.

A sixth aspect of the present invention is a magnetic head, comprising alower magnetic shield layer, a magnetoresistance effect device formed onthe lower magnetic shield layer through a lower reproduction magneticgap, the magnetoresistance effect device of the present invention, andan upper magnetic shield layer formed on the magnetoresistance effectdevice through an upper reproduction magnetic gap.

A seventh aspect of the present invention is a magneticrecording/reproducing head, comprising a reproducing head having amagnetic head of the present invention, a recording head having a lowermagnetic pole in common with the lower magnetic shield layer of themagnetic head, a record magnetic gap formed on the lower magnetic pole,an upper magnetic pole formed on the record magnetic gap, and a recordcoil for supplying a record magnetic field to the lower magnetic poleand the upper magnetic pole.

A eighth aspect of the present invention is a magnetic record mediumcomprising a substrate having a main surface, a base film having anamorphous layer and a metal crystal layer successively layered above themain surface of said substrate, a record layer formed on said base filmand composed of a hard magnetic film containing Co as a structuralelement, the hard magnetic film having a bi-crystal structure, and aprotection film formed on said record layer.

A ninth aspect of the present invention is a magnetic record medium,comprising a substrate having a main surface, a base film having a metalcrystal layer formed on the main surface of said substrate, and a mixinglayer between said substrate and said metal crystal layer and containingstructural elements of the substrate and structural element of the metalcrystal layer, a record layer formed on said base film and composed of ahard magnetic film containing Co as a structural element, the hardmagnetic film having a bi-crystal structure, and a protection filmformed on said record layer.

A tenth aspect of the present invention is a magnetic storing apparatus,comprising the magentoresistance effect device of the present invention,a write electrode for storing information to the magnetoresistanceeffect film of the magnetoresisitance effect device, and a readelectrode, composed of the electrode of the magentoresistance effectdevice, for reproducing information stored in the magnetoresistanceeffect film.

According to the present invention, the metal crystal layer as a basefilm (crystal metal base film) of a hard magnetic film containing Co asa structural element (Co type hard magnetic film) is disposed on areactive amorphous layer or an actively formed amorphous layer. Thus,the bonding energy of the crystal metal base film to the amorphous layeris larger than the condensation energy of the crystal grains thereof.The crystal metal base film has large crystal grains whose diameters arefor example five times or more the film thickness thereof. In addition,when a metal material such as Cr or V having a bcc structure is used fora crystal metal base film, the plane (110) that is the densest plane ofthe bcc structure grows with a priority. Moreover, the crystal metalbase film has a bcc (200) orientation component.

As described above, when a Co type hard magnetic film is formed on theabove-described crystal metal base film, the magnetic characteristicssuch as the coercive force, residual magnetization, saturatedmagnetization, and square ratio of the Co type hard magnetic film can beimproved. In addition, the crystal metal base film whose crystal grainsare sufficiently enlarged against the film thickness has excellentsurface flatness. Thus, the surface flatness of the Co type hardmagnetic film that is epitaxially formed with crystal grains of thecrystal metal base film can be improved.

In particular, when the Co type hard magnetic film has the bi-crystalstructure, the coercive force can be remarkably improved. In addition,the residual magnetization and square ratio can be improved. The crystalmetal base film disposed on the amorphous layer remarkably improves thereproducibility of the Co type hard magnetic film having the bi-crystalstructure. The bi-crystal structure is a crystal structure of which aplurality of sub-grains are present in one main-grain. In onemain-grain, the axis c of the sub-grains is oriented to the surface. Inaddition, the surface components of the axis c are almostperpendicularly disposed (80 to 100°). Thus, the sub-grains have a highanisotropic magnetic field Hk in the plane.

With the Co type hard magnetic film having such a bi-crystal structure,although it is a continuous film with a low isolation of themain-crystal grains, both large coercive force Hc and large residualmagnetization Mr can be satisfied. For example, while the coercive forceHc of the Co type hard magnetic film is 2000 Oe or more, the residualmagnetization Mr thereof can be 650 emu/cc or more. In addition, thesquare ratio S can be for example 0.9 or more. In the bi-crystalstructure, even if the diameters of main-grains are large, the smallestmagnetic grains are sub-grains therein. Consequently, problems in theconventional hard magnetic film that the film did not have excellentcrystal characteristics when crystal grains are small can be overcomeeasily in the present invention.

When the above-described Co type hard magnetic film is used for the biasmagnetic field applying film of the magnetoresistance effect device, thesufficient bias magnetic field can be obtained without need to increasethe film thickness of the Co type hard magnetic film. Thus, theBarkhausen noise can be effectively suppressed. When the Co type hardmagnetic film is used for a record layer of a magnetic record medium,with a thin Co type hard magnetic film, good magnetic characteristicsand good surface flatness can be obtained. In particular, the value of(Mr·t) can be decreased. Thus, in high density recording, a noise can bedecreased.

Further, a substrate according to the present invention is not only baresubstrate and includes substrate having various function layers on amain surface thereof. For example, the substrate is produced by formingcompound layers such as oxide layer, nitride layer, carbide layer andthe like or function layer such as gap layer for magnetic head on thesurface of bare substance such as Al₂O₃.TiC substrate, glass substrate,NiP substrate, Al substrate, Si substrate and the like.

These and other objects, features and advantages of the presentinvention will become more apparent in light of the following detaileddescription of best mode embodiments thereof, as illustrated in theaccompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view showing the structure of a hard magnetic filmstructural body according to an embodiment of the present invention;

FIG. 2 is a sectional view showing the structure of a hard magnetic filmstructural body according to another embodiment of the presentinvention;

FIG. 3 is a schematic diagram showing a bi-crystal structure of a hardmagnetic film according to an embodiment of the present invention;

FIG. 4A and FIG. 4B are schematic diagrams showing a process for forminga crystal metal base film according to an embodiment of the presentinvention;

FIG. 5A and FIG. 5B are schematic diagrams showing a process for forminga crystal metal base film according to a compared example of the presentinvention;

FIG. 6 is a graph showing the relation between the power of a sputteretching process and the thickness of an amorphous layer according to anembodiment of the present invention;

FIG. 7 is a graph showing the relation between the thickness of anamorphous layer and a coercive force Hc according to an embodiment ofthe present invention;

FIG. 8 is a graph showing the relation between the power of a sputteretching process and a coercive force Hc according to an embodiment ofthe present invention;

FIG. 9 is a graph showing the relation between the power of a sputteretching process and a saturated magnetization Ms according to anembodiment of the present invention;

FIG. 10 is a graph showing the relation between the power of a sputteretching process and surface roughness according to an embodiment of thepresent invention;

FIG. 11 is a graph showing the relation between the power of a sputteretching process and the diameters of crystal grains of a Cr crystal filmaccording to an embodiment of the present invention;

FIG. 12 is a graph showing the relation between the power of a sputteretching process and the diameters of crystal grains of a CoPt filmaccording to an embodiment of the present invention;

FIG. 13 is a graph showing the relation between the power of sputteretching process and the average diameter of crystal grains of a CoPtfilm according to an embodiment of the present invention;

FIG. 14 is a graph showing the relation between the power of a sputteretching process and a square ratio according to an embodiment of thepresent invention;

FIG. 15 is a schematic diagram showing the relation between a backpressure and a coercive force Hc in a spatter forming process accordingto an embodiment of the present invention;

FIG. 16 is a schematic diagram showing the relation between the power ofa spatter etching process and the thickness of a reactive crystal layeraccording to an embodiment of the present invention;

FIG. 17 is a TEM phot showing a section of a hard magnetic filmstructural body according to an embodiment of the present invention;

FIG. 18 is a TEM photo showing a plane of a hard magnetic filmstructural body according to an embodiment of the present invention;

FIG. 19 is a schematic diagram of the TEM photo shown in FIG. 17;

FIG. 20 is a schematic diagram of the TEM photo shown in FIG. 18;

FIG. 21 is a TEM photo showing a section of a hard magnetic filmstructural body according to a compared example of the presentinvention;

FIG. 22 is a TEM photo showing a plane of a hard magnetic filmstructural body according to a compared example of the presentinvention;

FIG. 23 is a schematic diagram of the TEM photo shown in FIG. 21;

FIG. 24 is a schematic diagram of the TEM photo shown in FIG. 22;

FIG. 25 is a graph showing the relation between the film thickness of acrystal metal base film and a coercive force Hc of a hard magnetic filmaccording to an embodiment of the present invention;

FIG. 26 is a graph showing the relation between the film thickness of acrystal metal base film and a saturated magnetization Ms of a hardmagnetic film according to an embodiment of the present invention;

FIG. 27 is a graph showing the relation between the film thickness of ahard magnetic film formed on Cr film and a coercive force Hc, a squareratio S of the hard magnetic film according to an embodiment of thepresent invention;

FIG. 28 is a sectional view showing the structure of a magnetoresistanceeffect device, a magnetic head, and a magnetic recording/reproducinghead according to a first embodiment of the present invention;

FIG. 29 is a sectional view showing a practical structure of a spinvalve film of the magnetoresistance effect device shown in FIG. 28;

FIG. 30 is a sectional view showing the structure of a magnetoresistanceeffect device, a magnetic head, and a magnetic recording/reproducinghead according to a second embodiment of the present invention;

FIG. 31 is a graph showing the relation between the film thickness of acrystal metal base film of the magnetic head shown in FIG. 30 andBarkhausen noise;

FIG. 32 is a graph showing the relation between a residual magnetizationMr of a hard magnetic film of the magnetic head shown in FIG. 30 andBarkhausen noise;

FIG. 33 is a sectional view showing the structure of a magnetic recordmedium according to an embodiment of the present invention;

FIG. 34 is a sectional view showing the structure of a modification of amagnetic record medium shown in FIG. 33;

FIG. 35 is a sectional view showing the structure of a magnetic storingapparatus according to an embodiment of the present invention;

FIG. 36 is a sectional view showing an example of the structure of aconventional magnetoresistance effect head;

FIG. 37 is a sectional view showing another example of the structure ofthe conventional magnetoresistance effect head; and

FIG. 38 is a graph showing characteristics of a hard magnetic film thatis a laminate film of a hard magnetic film and a magnetic sensiblephase.

DESCRIPTION OF PREFERRED EMBODIMENTS

Next, embodiments of the present invention will be described.

First of all, a hard magnetic film structural body according to anembodiment of the present invention will be described. FIG. 1 is asectional view showing the structure of a hard magnetic film structuralbody according to an embodiment of the present invention. The hardmagnetic film structural body according to the present invention can beapplied to for example a bias magnetic field applying film of amagnetoresistance effect device and a record layer of a magnetic recordmedium. In other words, the hard magnetic film structural body accordingto the present invention can be applied to other purposes.

In FIG. 1, reference numeral 11 is a substrate. A surface layer 12 isdisposed on the main surface of the substrate 11. The surface layer 12is composed of a non-magnetic and insulating compound such as a metaloxide or a metal nitride. Examples of the compound are alumina (AlOx),silica (SiOx), zirconia (ZrOx), titania (TiOx), tantalum oxide (TaOx),and titanium nitride (TiN).

The structural material of the substrate 11 is selected corresponding toan application for use. When the hard magnetic film structural body isused for a bias magnetic field applying film of a magnetoresistanceeffect device, an Al₂O₃.TiC substrate or the like is used for thesubstrate 11. When the hard magnetic film structural body is used for amagnetic record medium, a glass substrate, a NiP substrate, an Alsubstrate, or the like is used for the substrate 11.

The surface layer 12 contributes not only providing the main surface ofthe substrate 11 with non-magnetic and insulating characteristics, butforming a reactive amorphous layer on the main surface of the substrate11 as will be described later. In the magnetoresistance effect device, agap film may be used for the surface layer 12. In addition, anotherlayer may be disposed between the substrate 11 and the surface layer 12.The thickness of the surface layer 12 is preferably in the range from 10to 100 nm although it depends on the application for use.

A crystal metal base film 16 is formed on the surface layer 12 through areactive base film 15 that has a reactive amorphous layer 13 and areactive crystal layer 14. The crystal metal base film 16 controls thecrystal orientation of the hard magnetic material that contains Co as astructural element. In other words, the reactive amorphous layer 13, anda metal crystal layer composed of the reactive crystal layer 14, and thecrystal metal base film 16 is formed on the surface layer 12. A hardmagnetic film 17 that contains Co as a structural element (hereinafter,the hard magnetic film 17 is referred to as a Co type hard magneticfilm) is formed on the crystal metal base film 16. The reactiveamorphous layer 13, the reactive crystal layer 14, and the crystal metalbase film 16 compose a base film 18 of the Co type hard magnetic film17.

The crystal metal base film 16 is preferably composed of a crystal metalmaterial having a bcc structure so as to orient the axis c of the Cotype hard magnetic film 17 in the surface and to obtain a bi-crystalstructure (that will be described later). The crystal metal base film 16composed of a metal material having the bcc structure preferably has notonly the plane (110) (which is the densest plane of the bcc structure)and a bcc (200) orientation component. Examples of the structuralmaterial of the crystal metal base film 16 are crystal metals such asCr, V, Ti, Ta, W, Zr, Nb, Hf, Mo, and Al or alloys thereof. Among them,Cr, V, or an alloy thereof is more preferably used.

According to the present invention, the total film thickness of thecrystal metal base film 16 and the reactive base film 15 is as thin as50 nm or less. With such a thin base film 18, a Co type hard magneticfilm 17 having excellent magnetic characteristics can be obtained.However, when the film thickness of the base film 18 is too small, theeffect of the Co type hard magnetic film 17 cannot be effectivelyobtained. Thus, the total film thickness of the base film 18 ispreferably in the range from 5 to 50 nm.

The average diameter of crystal grains of the crystal metal base film 16is preferably five times or more the film thickness thereof. The averagediameter of the crystal grains the crystal metal base film 16 ispreferably in the range from 50 to 100 nm. The crystal metal base film16 whose crystal grains are enlarged is obtained with an amorphous layeras a base layer such as the reactive amorphous layer 13. When thecrystal grains of the crystal metal base film 16 are enlarged and suchcrystal grains are well oriented, the Co type hard magnetic film 17 canbe formed in the bi-crystal structure with high reproducibility. Whenthe base film 16 has the bcc (200) orientation component, thereproducibility of the bi-crystal structure is further improved. Inaddition, since the crystal metal base film 16 having the averagediameter of crystal grains that is five times or more the film thicknessof the front surface is a semi-epitaxial film, the surface flatness canbe remarkably improved.

The reactive base film 15 having the reactive amorphous layer 13 and thereactive crystal layer 14 is obtained when for example the crystal metalbase film 16 is formed on the surface layer 12 such as alumina andthereby they react. Thus, the reactive amorphous layer 13 and thereactive crystal layer 14 contain structural elements of the surfacelayer 12 and structural elements of the crystal metal base film 16. Inother words, a mixing layer (13, 14) is formed between the surface layer12 and the crystal metal base film 16, the mixing layer containsstructural elements of the surface layer 12 and the crystal metal basefilm 16. When the surface layer 12 is composed of alumina and thecrystal metal base film 16 is composed of Cr, the reactive amorphouslayer 13 and the reactive crystal layer 14 (mixing layer) contain bothAl and O or one of them and Cr.

The reactive crystal layer 14 is formed corresponding to the reactingstate of the surface layer 12 and the crystal metal base film 16. Thus,the reactive crystal layer 14 may be not formed depending on the surfacecondition of the surface layer 12 and the forming condition of thecrystal metal base film 16. The reactive base film 15 has at least thereactive amorphous layer 13.

The reactive amorphous layer 13 contributes to enlarging and orientingthe crystal grains of the crystal metal base film 16, flattening thesurface thereof, and forming the Co type hard magnetic film 17 havingthe bi-crystal structure. The amorphous layer composing a part of thebase film may be an amorphous layer 19 formed by the sputtering processas shown in FIG. 2 as well as the reactive amorphous layer 13. A metalcrystal layer 20 is formed as a crystal metal base on the amorphouslayer 19.

The structural material of the amorphous layer 19 may be the same as thestructural material of the reactive amorphous layer 13. Alternatively,the amorphous layer 19 may be an amorphous magnetic layer such as aCoZrNb amorphous layer. The metal crystal layer 20 may be a crystalmagnetic layer such as a CoZrNb crystal layer as well as a metalmaterial having the bcc structure. The CoZrNb amorphous layer can beformed with a sputtering target CoZrNb of which the content of Co isless than 90%. In addition, the CoZrNb crystal layer is formed with asputtering target CoZrNb of which the content of Co is 90% or more. Theamorphous layer 19 and the metal crystal layer 20 compose the base film18 of the Co type hard magnetic film 17.

As a necessary condition, the amorphous layer that composes a part ofthe base film 18 of the reactive amorphous layer 13 and the amorphouslayer 19 is an equal film. The film thickness of the amorphous layer isaround several nm. In reality, the film thickness of the amorphous layeris preferably 2 nm or more. When the film thickness of the amorphouslayer is less than 2 nm, the equality of the film may be degraded. Inthe present invention, the amorphous layer represents a non-crystalsolid state of which atoms or molecules are not regularly and spatiallydisposed.

The Co type hard magnetic layer 17 preferably has the bi-crystalstructure shown in FIG. 3. The thickness of the Co type hard magneticlayer 17 is preferably in the range from 5 to 150 mm. The bi-crystalstructure is a crystal structure of which a plurality of sub-grain S ispresent in one main-grain M. The axis c of the sub-grains S is orientedin the surface in one main-grain M. The surface components of the axis care nearly perpendicularly disposed (80 to 100). The Co type hardmagnetic layer 17 has Co(110) oriented perpendicular to the surfacethereof. Thus, the sub crystal gain S has a large anisotropic magneticfield Hk in the surface, thereby increasing the coercive force Hc andthe residual magnetization Mr of the Co type hard magnetic film 17.

When the Co type hard magnetic film 17 has the bi-crystal structure,although the film is a continuous film with a low isolation of themain-grains M, the Co type hard magnetic film 17 that has a largecoercive force Hc and a large residual magnetization Mr can be obtained.When the film thickness of the Co type hard magnetic film 17 is in therange from 5 to 30 nm, while the coercive force H is 2000 Oe or more,the residual magnetization Mr can be 650 emu/cc or more. In addition,the square ratio S of the Co type hard magnetic film 17 is as large as0.9 or more.

In particular, when the Co type hard magnetic film 17 is used for a biasmagnetic applying film of a magnetoresistance effect device, thesub-grains S with a large anisotropic magnetic field Hk prevents themagnetization reversal of the hard magnetic film. When the magneticsensible layer and the hard magnetic film exchange-bond at the interfacethereof, the direction of the magnetization of the hard magnetic layeris not easily reversed by the magnetization reversal of the magneticsensible layer. Thus, the Barkhausen noise can be suppressed.

In the above-described bi-crystal structure, the diameters of themain-grains M are preferably in the range from 50 to 100 nm. Inaddition, the diameters of the sub-grains S are preferably in the rangefrom 10 to 30 nm. When the diameters of the main-grains M that have abasic function of crystal grains of a crystal film are increased to 50to 100 nm, the surface flatness of the Co type hard magnetic film 17 canbe improved. In addition, the sub-grains S provide the above-describedexcellent magnetic characteristics. Moreover, since the sub-grains Shave a function of magnetic grains, when the Co type magnetic film 17 isused for a record layer of a magnetic record medium, the noise can bedecreased in high density recording.

The structural material of the Co type hard magnetic film 17 is notlimited. Instead, a variety of hard magnetic materials containing Co asa structural element can be used. These materials can be selectedcorresponding to the application of the Co type hard magnetic film 17.Practical examples of the material of the Co type hard magnetic film 17are CoCrTaPt, CoCrTa, CoPt, CoCr, and Co. When the Co type hard magneticfilm 17 is used for a bias magnetic field applying film of amagnetoresistance effect device, CoPt with a large residualmagnetization Mr is preferably used. When the Co type hard magnetic film17 is used for a record layer of a magnetic record medium, a Co groupalloy containing a non-magnetic metal is preferably used. Thenon-magnetic element contained in the Co group alloy is deposited in thegrain boundary of the sub-grains S and thereby the sub-grains S aremagnetically isolated.

The film thickness of the Co type hard magnetic film 17 is properlyselected corresponding to the application for use. When the Co type hardmagnetic film 17 is used as a bias magnetic field applying film of amagnetoresistance effect device, the film thickness of the Co type hardmagnetic film 17 is preferably in the range from 10 to 100 nm. When thefilm thickness of the Co type hard magnetic film 17 is less than 5 nm,even if the film has the bi-crystal structure, a sufficient biasmagnetic field may not be obtained. On the other hand, when the filmthickness of the Co type hard magnetic film 17 exceeds 150 nm, astructural problem of the device may take place. Even if the filmthickness of the Co type hard magnetic film 17 is 100 nm or less, asufficient bias magnetic field can be obtained. When the Co type hardmagnetic film 17 is used for a record layer of a magnetic record medium,the film thickness of the Co type hard magnetic film 17 is preferably 10nm or less. When the film thickness t of the Co type hard magnetic film17 is 10 nm or less, the value of (Mr·t) decreases, thereby decreasingthe noise.

Next, a process for forming a crystal metal base film 16 whose crystalgrain diameters are enlarged (and a metal crystal layer 19) and aprocess for forming a Co type hard magnetic film 17 having a bi-crystalstructure will be described.

For example, when the bond energy of the surface layer 12 (on thesubstrate 11 side) and the crystal metal base film 16 is increased, thediameters of the crystal grains of the crystal metal base film 16 can beenlarged. The increase of the bond energy accelerates the reaction ofthe surface layer 12 and the crystal metal base film 16, thereby forminga reactive amorphous layer 13. The surface layer 12 is preferablycomposed of a metal oxide or a metal nitride so as to accelerate thereaction with the crystal metal base film 16 and form the amorphouslayer. The method for forming the reactive amorphous layer 13 will bedescribed later in detail.

When the metal crystal layer is deposited as the crystal metal base film16 on the reactive amorphous layer 13, large crystal grains 16 a asshown in FIG. 4A are produced because the bond energy with the reactiveamorphous layer 13 is larger than the condensation energy of the crystalgrains of the crystal metal base film 16. With the diameters of thecrystal grains maintained, the film is further formed. Thus, as shown inFIG. 4B, a crystal metal base film 16 with crystal grains whosediameters 16 a are five times or more or 10 times or more the filmthickness thereof can be obtained. In a crystal growth of which thecrystal grains are much enlarged in comparison with the film thickness,the surface flatness is remarkably improved. In FIG. 4A and FIG. 4B,reference numeral 16 b is a crystal boundary. In FIG. 4A and FIG. 4B,the reactive crystal layer 14 is not shown.

As shown in FIG. 2, this applies to the case that an amorphous layer 19has been formed on the surface layer 12 by the sputtering process or thelike. When a metal crystal layer 20 is formed on the amorphous layer 19that is subject to reaction, the diameters of crystal grains and thecrystal orientation of the metal crystal layer 20 are largely affected.In other words, since the bond energy of the amorphous layer 19 and themetal crystal layer 20 becomes larger than the condensation energy ofthe crystal grains of the metal crystal layer 20, a metal crystal layer20 with crystal grains whose diameters are five times or more or tentimes or more the film thickness thereof is obtained.

In the conventional process for forming the metal crystal layer, a metalmaterial 20′ deposited on the surface layer 12 has diameters of crystalgrains that are similar to the film thickness as shown in FIG. 5A. Sincethe crystal grains gradually grow, as shown in FIG. 5B, only the metalcrystal layer 20′ with crystal grains whose diameters are 10 nm or lessis obtained. According to the present invention, with theabove-described effects of the reactive amorphous layer 13 and theamorphous layer 19, the crystal grains of the crystal metal base film 16and the metal crystal layer 20 can be satisfactorily enlarged.

When a metal material with the bcc structure is used for the crystalmetal base film 16 and the metal crystal layer 20, with the increase ofthe bond energy at each interface, both the normal bcc (100) prioritygrowth and the bcc (200) orientation tend to take place. In the initialgrowth mode, Cr or the like tends to grow in bcc (200) orientation.Thus, when the film thicknesses of the crystal metal base film 16 andthe metal crystal layer 20 are decreased, the bcc (200) orientationcomponents can be increased. The crystal metal base film 16 and themetal crystal layer 20 according to the present invention have anorientation plane of which the bcc (110) plane and the bcc (200) planeare mixed.

The Co type hard magnetic film 17 formed on the crystal metal base film16 with enlarged crystal grains and a high orientation or the metalcrystal layer 20 have the bi-crystal structure. The bcc (200)orientation components of the crystal metal base film 16 or the metalcrystal layer 20 largely contribute to the bi-crystal structure of theCo type hard magnetic film 17. With the crystal metal base film 16 orthe metal crystal layer 20 having enlarged crystal grains and bcc (200)orientation components, the bi-crystal structure of the Co type hardmagnetic film 17 can be obtained with high reproducibility.

The Co type hard magnetic film 17 having the bi-crystal structure can beobtained without need to heat the substrate and perform a heattreatment. The film thickness of the bi-crystal structure of aconventional magnetic record medium is obtained by the sputteringprocess while a single crystal substrate is heated at around 300° C. Inthe present invention, the substrate may be heated.

Next, a method for forming a reactive amorphous layer 13 will bedescribed. To form the reactive amorphous layer 13, it is necessary toimprove the reactivity of a surface layer 12 of the substrate 11. Inreality, the surface treatment such as the sputter etching process isperformed on the surface layer 12 so as to physically dissociate aterminal element such as oxygen or hydrogen and thereby form a free bondhand on the front surface. To form such a free bond hand on the frontsurface, a metal oxide or a metal nitride is preferably used for thesurface layer 12.

When an alumina (AlOx) film is used for the surface layer 12, the bondhand of Al is terminated with oxygen, hydrogen, or the like on the frontsurface of the AlOx film. Thus, when the sputter etching process isperformed for the AlOx film at a high power, a free bond hand of Almissing oxygen is formed. When a Cr film is formed as the crystal metalbase film 16 on the AlOx film, Cr reacts with Al and thereby forming areactive amorphous layer 13 containing Cr and Al. In addition, areactive crystal layer 14 is formed.

Next, conditions of the sputter etching process will be described. Acase that after a spatter etching process is performed on a surfacelayer 12 composed of an AlOx film, a crystal metal base film composed ofa Cr film and a Co type hard magnetic film 17 composed of a CoPt filmare successively formed will be described.

FIG. 6 shows the relation between the power [W] of a sputter etchingprocess and the film thickness of a reactive amorphous layer. Althoughone type of metal (Cr) is sputter etched for a predetermined time period(three minutes), when the power of the sputter etching process to theAlOx film is increased, the film thickness of the reactive amorphouslayer can be controlled. In particular, from FIG. 6, it is clear thatwhen the power is 200 W or more, a nearly constant (around 2 nm) filmthickness can be obtained.

FIG. 7 shows the relation between the thickness of an amorphous layerand the coercive force Hc of a CoPt film. FIG. 8 shows the relationbetween the power of a sputter etching process and the coercive force Hcof a CoPt film. FIG. 9 shows the relation between the power of a spatteretching process and the saturated magnetization Ms of a CoPt film. Whenthe reactive amorphous layer is formed for around 2 nm (see FIG. 6),from FIG. 8 and FIG. 9, it is clear that both the coercive force Hc andthe saturated magnetization Ms become high.

FIG. 10 shows the relation between the power of a spatter etchingprocess and the surface flatness (Rmax) of a CoPt film. From FIG. 10, itis clear that by controlling the power of the sputter etching process,the film thickness of the amorphous film can be controlled and therebythe surface flatness of the CoPt film can be decreased. FIG. 11 showsthe relation between the power of a sputter etching process and thediameters of crystal grains of a Cr crystal film. FIG. 12 shows therelation between the power of a sputter etching process and thediameters of main-grains of a CoPt film. From FIG. 11 and FIG. 12, it isclear that when the power of the sputter etching process is 200 W ormore, an amorphous layer is formed and thereby the diameters of thecrystal grains of the Cr crystal film become large. Thus, it is clearthat the diameters of the main-grains of the CoPt film become large.From FIG. 13, it is clear that the CoPt film has a bi-crystal structure.

In addition, from FIG. 8 and FIG. 14, although the CoPt film has acoercive force as high as 2000 Oe, the square ratio S is as large as 0.9or more. This is because although the CoPt film is a continuous film ofwhich the main-grains are less isolated, sub-grains having a highcrystal magnetic anisotropy are perpendicularly disposed in the surfacedue to the bi-crystal structure. In such a bi-crystal structure, sincethe magnetization reversal of the adjacent main-grains is not affected,a high square ration S is obtained. In addition, as shown in FIG. 15,even if the back pressure at which the CoPt film is formed is as low as10⁻⁵ Torr, a high coercive force can be stably obtained.

FIG. 15 shows the relation between the power of a sputter etchingprocess and the thickness of a reactive crystal layer 14. From FIG. 15,it is clear that when the power of the sputter etching process is 200 W,the film thickness of the reactive crystal layer 14 can be decreased.

Next, a method for fabricating the hard magnetic film structural bodyshown in FIG. 1 will be described corresponding to the enlarging methodof crystal grains of the crystal metal base film 16, the method forforming the Co type hard magnetic film 17 with the bi-crystal structure,and the method for forming the reactive amorphous layer 13.

A surface layer 12 composed of a metal oxide or a metal nitride isformed on a substrate 11 by a sputtering process or the like. The filmforming chamber is opened. Thereafter, with another sputtering unit, astrong electric field of 200 W or more is applied to the front surfaceof the surface layer 12 and then sputter-etched with an inert gas suchas Ar ions, Kr ions, Xe ions, or He ions.

Thereafter, with a target composed of a metal or an alloy having a bccstructure, a crystal metal base film 16 is formed by an RF (RadioFrequency) magnetron spatter process. At this point, the above-describedexcellent characteristics are obtained without need to heat thesubstrate. However, the substrate is preferably heated. The reactiveamorphous layer 13, the reaction crystal layer 14, and the crystal metalbase film 16 are successively formed on the resultant surface layer 12.

Thereafter, a Co type hard magnetic film 17 is formed by a DC (DirectCurrent) magnetron sputtering process. The Co type hard magnetic film 17has a bi-crystal structure. As a result, the hard magnetic filmstructural body as shown in FIG. 1 can be obtained.

The hard magnetic film structural body shown in FIG. 2 is fabricated inthe following manner.

A surface layer 12 composed of a metal oxide such as alumina or a metalnitride is formed on a substrate 11 by a spatter process or the like.The film forming chamber is opened. Thereafter, with another sputteringunit, a strong electric field of 200 W or more is applied to the frontsurface of the surface layer 12 and then sputter-etched with an inertgas such as Ar ions, Kr ions, Xe ions, or He ions.

Next, with a target CoZrNb, an amorphous layer 19 composed of a CoZrNbamorphous is formed by an RF magnetron sputtering process. Thereafter,with a target CoZrNb having a different content of Co, a metal crystallayer 20 is formed. The metal crystal layer 20 may be a metal having abcc structure or an alloy thereof.

The amorphous layer 19 and the metal crystal layer 20 are preferablyformed in succession in a vacuum atmosphere at a time.

Next, a Co type hard magnetic film 17 is formed by a DC (Direct Current)magnetron sputtering process. Thus, the Co type hard magnetic film 17has a bi-crystal structure. As a result, the hard magnetic filmstructural body as shown in FIG. 2 is obtained.

Next, a practical example of the hard magnetic film structural bodyfabricated according to the above-described embodiment will bedescribed. As structural materials of the individual layers of the hardmagnetic film structural body, a surface layer 12 on the substrate 11side is composed of an AlOx film. A crystal metal base film 16 iscomposed of a Cr film. A Co type hard magnetic film 17 is composed of aCoPt film. The film forming condition and the sputter etching conditionof the hard magnetic film structural body are the same as thosedescribed above.

FIG. 17 and FIG. 18 are TEM (Transmission Electron Microscope) photosshowing a section and a plane of a hard magnetic film structural bodythat has the structure shown in FIG. 1 and that is fabricated by theabove-described fabrication method. FIG. 19 is a schematic diagram ofthe TEM photo shown in FIG. 17. FIG. 20 is a schematic diagram of theTEM photo shown in FIG. 18.

From FIG. 17, it is clear that the base film 18 has a three-layerstructure of a reactive amorphous layer 13, a reactive crystal layer 14,and a Cr crystal film (crystal metal base film) 16 disposed in the orderon a surface layer 12 of the substrate 11. From FIG. 18, it is clearthat the average diameter of the main-grains M of the CoPt film 17 is aslarge as 50 nm to 100 nm. Sub crystal gains S are formed in themain-grains M. Thus, it is clear that the CoPt film 17 has a bi-crystalstructure. In each main-grain M, surface components of the axis c of thesub-grains S are disposed almost perpendicularly (80 to 100°).

Due to the effect of the reactive amorphous layer 13, the averagediameter of grains of the Cr crystal film 16 as the crystal metal basefilm is not around 10 nm or less (namely, not fine crystal grains) andthe crystal grains whose grain diameters are as large as five times ormore the film thickness thereof (around 2 nm) are well oriented anddisposed. In addition, orientation components of bcc (200) of the Crcrystal film 16 largely affect the bi-crystal structure.

When the surface flatness of the Cr crystal film 16 was measured by anAFM (Atomic Force Microscope), the maximum value Rmax of the surfaceflatness is as large as 0.8 nm or less (namely, the Cr crystal film 16has a high surface flatness). Likewise, the surface flatness of the CoPtfilm 17 is also excellent.

FIG. 21 and FIG. 22 are TEM photos showing a section and a plane of ahard magnetic film structural body according to a compared example ofthe present invention. FIG. 23 is a schematic diagram of the TEM photoshown in FIG. 21. FIG. 24 is a schematic diagram showing the TEM photoshown in FIG. 22. In the compared example, a reactive crystal layer 14′and a Cr crystal film 16′ are formed as a base film on the AlOx film 12.A CoPt film 17′ is formed on such a base film.

In the Cr crystal film 16′ of the compared example, the average diameterof crystal grains is in the range from 10 to 20 nm that is smaller thanfive times the film thickness thereof. The roughness of the interface tothe CoPt film 17′ is large. The diameters of crystal grains of the CoPtfilm 17′ are as small as 10 to 20 nm. Measured results of an electrondiffraction pattern show that the crystal orientation of the CoPt film17′ of the compared example is completely different from the crystalorientation of the CoPt film 17 of the embodiment. In addition, the CoPtfilm 17′ does not have the bi-crystal structure. Moreover, the coerciveforce Hc of the CoPt film 17′ is as low as 600 Oe.

A section of the hard magnetic film structural body that has thestructure shown in FIG. 2 and that has been fabricated by theabove-described fabrication method was observed by a TEM. The observedresults show that a base 18 has a two-layer structure of an amorphouslayer 19 and a metal crystal layer 20. In addition, a section of thefront surface of the CoPt film as the hard magnetic film 17 was observedby the TEM. The observed results show that the average diameter ofcrystal grains of the CoPt film is as large as 50 nm or more and 100 nmor less. As a reason why such a crystal was obtained, the amorphouslayer 19 cause the diameters of grains of the metal crystal layer 20 tobecome as large as 10 nm or less that are much larger than the filmthickness thereof and thereby the crystal grains to be well oriented.With the metal crystal layer 20 that has been well oriented, a CoPt filmhaving a bi-crystal structure is obtained.

Next, magnetic characteristics of the Co type hard magnetic film 17 ofthe hard magnetic film structural body according to the embodiment willbe described in detail.

Although the film thickness of the Co type hard magnetic film 17 of thehard magnetic film structural body of the present invention is small,the film 17 has excellent magnetic characteristics of which the coerciveforce Hc is around 2200 Oe or more and the residual magnetization Mr isaround 900 emu/cc or more. In addition, the Co type hard magnetic film17 has a bi-crystal structure. The square ratio S of the Co type hardmagnetic film 17 is as large as 0.9 or more. With a large square ratio,a hard magnetic film that is used in a residual magnetization state as abias film is obtained.

It is supposed that these excellent characteristics largely depend on acombination of materials of the substrate 11 (including the surfacelayer 12). Table 1 shows the relation among combinations of materials ofthe substrate 11 (including the surface layer 12) and the crystal metalbase film 16 (or the metal crystal layer 20), the coercive force Hc ofthe Co type hard magnetic film 17, and the saturated magnetization Msthereof.

The base metals shown in Table 1 are the crystal metal base film 16. Thereactive amorphous layer 13 contains these metals and the structuralelements of the materials of the substrate.

TABLE 1 Saturated Material of substrate Coercive force magnetization(including surface layer) Base metal Hc (Oe) Ms (emu/cc) AlOx 100 nm Cr2200 900 T-SiO₂ 1000 820 Si (100) 2000 910 AlOx 100 nm V 2200 910 T-SiO₂1000 820 Si (100) 2000 920

As is clear from Table 1, when a substrate that has an alumina surfacelayer is used regardless whether the base metal is Cr or V, the highestcoercive force Hc can be obtained. With a Si (100) substrate, the nexthighest coercive force Hc can be obtained. With a combination of a Si(100) substrate and V, the highest saturated magnetization Ms isobtained. With a combination of a Si (100) substrate and V, the secondhighest saturated magnetization Ms is obtained. With a combination of analumina surface layer and V, the third highest saturated magnetizationMs is obtained.

Table 2 shows the relation among combinations of the CoZrNb amorphouslayer as the amorphous layer 19 and various metal crystal layers 20, thecoercive force Hc of the Co type hard magnetic film 17, and thesaturated magnetization Ms thereof. From Table 2, it is clear that thesaturated magnetization in the case that a Cr film as a base metal isformed on the CoZrNb amorphous layer is slightly superior to thesaturated magnetization in the case that a V film as a base metal isformed on the CoZrNb amorphous layer.

TABLE 2 Hard Coercive Saturated Amorphous Metal crystal magnetic forceHc magnetization layer layer film (Oe) (emu/cc) CoZrNb Cr (5 nm) CoPt1700 700 (2 nm) V (5 nm) (20 nm) 1700 720 Co93 (Zr, Nb) 7 1500 700 Co95(Zr, Nb) 5 1500 720 CoCr 1800 750

Table 3 shows the relation between the film thickness of the amorphouslayer and the diameters of crystal grains of the Cr base film. When theamorphous layer is not formed, the magnetic characteristics such ascoercive force Hc of the CoPt film are degraded. When the amorphouslayer is formed, the magnetic characteristics of the CoPt film areimproved.

TABLE 3 Thickness of Cr base film Amorphous Diameters of CrystalCharacteristics layer crystal grains orientation of CoPt film 20 nm  50to 100 nm bcc ⊚ None 10 to 20 nm bcc x

Table 4 shows the relation among combinations of major structuralelements of the base metal film and the hard magnetic film, coerciveforce Hc thereof, and saturated magnetization Ms thereof. In Table 4, analumina layer is disposed below the base metal film. In eachcombination, high magnetic characteristics can be obtained. Inparticular, when Cr or V is used for the base metal and CO₈₀Pt₂₀ film isused for the hard magnetic film, high coercive force Hc and highsaturated magnetization Ms are obtained.

TABLE 4 Saturated Base metal Hard magnetic Coercive force magnetizationfilm film Hc (Oe) Ms (emu/cc) Cr Co80Pt20 2200 900 Co75Cr13Pt12 2500 720Co75Cr13Ta12 2500 700 Co75Cr13Ta8Pt4 2550 700 V Co80Pt20 2200 920Co75Cr13Pt12 2500 740 Co75Cr13Ta12 2500 710 Co75Cr13Ta8Pt4 2560 740 TiCrCo80Pt20 2000 850 Co75Cr13Pt12 2200 780 Co75Cr13Ta12 2200 750Co75Cr13Ta8Pt4 2200 750 CrV Co80Pt20 2200 900 Co75Cr13Pt12 2300 800Co75Cr13Ta12 2300 780 Co75Cr13Ta8Pt4 2400 780 Ti Co80Pt20 1800 720 TaCo80Pt20 1800 720 W Co80Pt20 1800 700 Al Co80Pt20 2200 780 Zr Co80Pt202000 720 Nb Co80Pt20 1800 700 Hf Co80Pt20 1800 700 Mo Co80Pt20 1800 700

FIG. 25 and FIG. 26 show the dependency of these magneticcharacteristics to the thickness of the crystal metal base film 16 (orthe metal crystal layer 20). When the film thickness of the crystalmetal base film 16 (or the metal crystal layer 20) is 4 nm or more, thecoercive force Hc becomes around 2000 Oe and the saturated magnetizationMs is stably kept in the range from 850 to 950 emu/cc. Thus, thedependency of the film thickness of the base film is lost.

FIG. 27 shows the relation between the film thickness of a hard magneticfilm (CoPt film) formed on a Cr film (film thickness=5 nm) and Hc, S(square ratio) of CoPt film. The hard magnetic film (CoPt film) formedon the Cr layer (film thickness=5 nm) has a excellent square ratios.When the film thickness of the hard magnetic film is thin, the magneticcharacteristics of hard magnetic film are improved.

Next, with reference to FIG. 28, a record/reproduction separation typemagnetic head of which the magnetoresistance effect device according tothe present invention is used for a reproducing device portion will bedescribed as an embodiment of the present invention. FIG. 28 is asectional view showing the record/reproduction separation type magnetichead viewed from a medium opposite side (in the drawing, the directionof the axis x represents the direction of track width; the direction ofthe axis y represents the traveling direction of the record track).

In FIG. 28, reference numeral 21 is a substrate. The substrate 21 is forexample an Al₂O₃.TiC substrate having an Al₂O₃ layer. A lower magneticshield layer 22 is formed on the main surface of the substrate 21. Thelower magnetic shield layer 22 is composed of a soft magnetic materialsuch as NiFe alloy, FeSiAl alloy, or amorphous CoZrNb alloy. A lowerreproduction magnetic gap 23 is formed on the lower magnetic shieldlayer 22. The lower reproduction magnetic gap 23 is composed of anon-magnetic insulation material such as AlOx. The lower reproductionmagnetic gap 23 is equivalent to the surface layer 12 of theabove-described embodiment.

A spin valve GMR film 24 is formed as a magnetoresistance effect film onthe lower reproduction magnetic gap 23. A pair of bias magnetic fieldapplying films 25 are formed at an out-region of a track width (magneticfield detecting portion) between the spin valve GMR film 24 and thelower reproduction magnetic gap 23. The pair of bias magnetic fieldapplying films 25 are disposed at a predetermined interval. In otherwords, the spin valve GMR film 24 spreads on the pair of bias magneticfield applying film 25. The spin valve GMR film 24 and the bias magneticfield applying film 25 are exchange-coupling at the laminate portion.

As with the hard magnetic film structural body shown in FIG. 1, the biasmagnetic field applying film 25 is a laminate film of a reactive basefilm 15 (including a reactive amorphous layer), a crystal metal basefilm 16, and a Co type hard magnetic film 17. As with the hard magneticfilm structural body shown in FIG. 2, the bias magnetic field applyingfilm 25 may be a laminate film of an amorphous layer 19, a metal crystallayer 20, and a Co type hard magnetic film 17. These films arefabricated by the conditions and steps of the above-describedembodiment.

The laminate film of the spin valve GMR film 24 and the bias magneticfield applying film 25 may be structured by layering only both edgeportions of the spin valve GMR film 24 on the pair of bias magneticfield applying films 25. In this structure, at the portion where thebias magnetic field applying film 25 and the spin valve GMR film 24 arenot layered, the coercive force is not decreased. Thus, the coerciveforce of the bias magnetic field applying film 25 can be properlymaintained.

As a practical structure of the spin valve GMR film 24, a magneticmulti-layer film of a CoZrNb layer 241 with a film thickness of around10 nm, a NiFe layer 242 with a film thickness of around 2 nm, a CoFelayer 243 with a film thickness of around 3 nm, a Cu layer 244 with afilm thickness of around 3 nm, a CoFe layer 245 with a film thickness ofaround 2 nm, a IrMn layer 246 with a film thickness of around 8 nm, anda Ta layer 247 with a film thickness of around 10 nm disposed in theorder from the substrate side.

A pair of lead electrodes 26 are formed on the spin valve GMR film 24.With the interval of the pair of lead electrodes 26, the substantialreproduction track width of the spin valve GMR film 24 is defined. Thelead electrodes 26 is a laminate film of for example a Ta layer, a Culayer, and a Ta layer. The spin valve GMR film 24, the pair of biasmagnetic field applying films 25, and the pair of lead electrodes 26compose an overlaid structure GMR reproducing device portion 27.

An upper magnetic shield layer 29 is formed on the GMR reproducingdevice portion 27 through an upper reproducing magnetic gap 28. Theupper reproducing magnetic gap 28 is composed of a non-magneticinsulation material that is the same as the material of the lowerreproducing magnetic gap 23. The upper magnetic shield layer 29 iscomposed of a soft magnetic material that is the same as the material ofthe lower magnetic shield layer 22. Thus, a shield type GMR head 30 as areproducing head is structured.

A thin film magnetic head 31 is formed as a recording head on the shieldtype GMR head 30. A lower record magnetic pole of the thin film magnetichead 31 is composed of a magnetic layer that is the same as the uppermagnetic shield layer 29. In other words, the upper magnetic shieldlayer 29 of the shield type MR head 30 is in common with the lowerrecord magnetic pole of the thin film magnetic head 31. A recordmagnetic gap 32 and an upper record magnetic pole 33 are successivelyformed on the lower record magnetic pole 29 that is common with theupper magnetic shield layer. The record magnetic gap 32 is composed of anon-magnetic insulation material such as AlOx. A recording coil (notshown) that applies a record magnetic field to the lower record magneticpole 29 and the upper record magnetic pole 33 is formed at the rear ofthe medium opposite surface. Thus, a thin film magnetic head 31 isstructured as a recording head.

Since the coercive force Hc of the Co type hard magnetic film 17 ishigh, the shield type GMR head 30 according to the embodiment issuitable for the above-described low floating state and contacttraveling state. In particular, in the exchange-bonding type, thecoercive force Hc of the MR head is lower than the coercive force of thehard magnetic film (see FIG. 38). Thus, it can be said that the Co typehard magnetic film with the coercive force Hc according to the presentinvention can be preferably used.

In a conventional hard magnetic film with a small saturatedmagnetization Ms, because of the exchange-bonding with the magneticsensible layer of the spin valve GMR film, the total coercive force Hcof the hard magnetic film and the magnetic sensible layer is 800 Oe whenthe film thickness thereof is 20 nm. However, in the Co type hardmagnetic film 17 according to the embodiment, the coercive force Hc isas high as 2200 Oe and the saturated magnetization Ms is as high as 900emu/cc. Thus, even if the film thickness of the Co type hard magneticfilm is around 20 nm, the total coercive force Hc of the magneticsensible layer of the spin valve GMR film 24 and the Co type hardmagnetic film 17 is around 1100 Oe.

In addition, according to the embodiment, the residual magnetization Mris as high as around 800 emu/cc and the square ratio S is as large as0.9 or more. Thus, the Co type hard magnetic film is not subject to themagnetic field of the magnetic record medium. Thus, a stable and largebias magnetic field is obtained. Table 5 shows the degradation amount ofthe residual magnetization Mr of the Co type hard magnetic film in thecase that an AC magnetic field of −400 to +400 Oe is applied to the Cotype hard magnetic film 17 according to the embodiment in the samedirection as the magnetic field of the medium. From Table 5, it is clearthat with a large angular ratio S, the long time reliability of theresidual magnetization Mr of the Co type hard magnetic film isremarkably improved.

TABLE 5 Co type hard magnetic Co type hard film of magnetic film ofpresent invention compared example (square ratio = 0.9) (square ratio =0.8) Initial Mr after magnetized 800 emu/cc 600 emu/cc Mr after ACmagnetic field 800 emu/cc 520 emu/cc is applied

In this embodiment, after the Co type hard magnetic film 17 is formed,the partial region of the Co type hard magnetic film 17 and the basefilms 15 and 16 is removed by the ion milling process or the like. Thus,the front surface of the AlOx film 23 is exposed. The spin valve GMRfilm 24 is formed on the open portion of the AlOx film 23 and the Cotype hard magnetic film. The surface pattern of the Co type hardmagnetic film 17 is transferred to the front surface of the AlOx film 23that has been exposed by the ion milling process. However, as describedabove, since the surface roughness of the Co type hard magnetic film 17is small, the surface roughness due to the transferred pattern is alsosmall. Thus, the magnetic characteristics of the spin valve GMR film 24formed on the Co type hard magnetic film 17 are not largely affected.

Table 6 shows the relation among the coercive force Hc in the directionof the difficult axis of the magnetic sensible layer, the inter-layercoupling magnetic field Hin of the magnetic sensible layer and the fixedmagnetization layer, and the surface roughness (Rmax) for the spin valveGMR film 24 according to the embodiment and a spin valve GMR filmaccording to a compared example of which a surface roughness (Rmax) isformed by a sputtering process on the front surface of the CoPt filmbefore an ion milling process is performed. From Table 6, it is clearthat the inter-layer coupling magnetic field Hin that affects the biaspoint to be designed can be sufficiently suppressed when the surfaceroughness (Rmax) is 1 nm or less. Since the coercive force Hc and theinter-layer coupling magnetic field Hin directly affect the occurrenceof the Barkhausen noise, the coercive force Hc and the inter-layercoupling magnetic field Hin are preferably 2 Oe or less and 10 Oe orless, respectively.

TABLE 6 Surface roughness of CoPt film before Inter-layer millingprocess · Coercive force coupling magnetic Rmax (nm) Hc (Oe) field Hin(Oe) 0.8 0.1 3.9 8 3 11

Table 7 shows the relation among the film thickness of the crystal metalbase film 16 (for example, a Cr film), the coercive force Hc in thedirection of the difficult axis of the magnetic sensible layer, and theinter-layer coupling magnetic field Hin of the magnetic sensible layerand the fixed magnetization layer. When the film thickness of thecrystal metal base film 16 is small, the surface roughness after themilling process can be suppressed. Thus, it is clear that Hc and Hin ofthe spin valve film can be suppressed. When the magnetic characteristicsare improved, as shown in Table 8, the probability of the occurrence ofthe Barkhausen noise is the lowest even if the film thickness is around6 nm. In the exchange-coupling type, when the film thickness of the basemetal film is large, there is a large gap in a joint region with thehard magnetic film. Thus, the bias magnetic field to the magneticsensible layer weakens. With the hard magnetic film that is thin andthat has a high saturated magnetization Ms according to the embodiment,it is not necessary to thicken the film to prevent the coercive force Hcfrom decreasing. Thus, the decrease of the effective bias to themagnetic sensible layer due to the gap can be prevented.

TABLE 7 Coercive force Hc in direction of Film thickness of difficultaxis of Inter-layer Cr crystal film magnetic sensible coupling magnetic(nm) layer (Oe) field Hin (Oe) 0 0.1 3.9 20 1.0 —

TABLE 8 Film thickness of Cr crystal Probability of occurrence of film(nm) Barkhausen noise (%) 0 15 6 2 20 15

Next, with reference to FIG. 30, an abutted junction typemagnetoresistance effect device according to an embodiment of thepresent invention will be described. The magnetoresistance effect headaccording to the embodiment has the Co type hard magnetic film 17according to the first embodiment as a hard bias film. As shown in FIG.30, Co type hard magnetic films 17 are adjacently disposed on both sidesof a spin valve GMR film 24. A base film of the Co type hard magneticfilm 17 is the same as the base film of the first embodiment. The otherportions of the Co type hard magnetic film 17 are the same as thoseshown in FIG. 28. FIG. 30 shows a record/reproduction separation typemagnetic head having a shield type GMR head 30 as a reproducing head anda thin film magnetic head 31 as a recording head.

According to the magnetoresistance effect head of the embodiment, exceptfor the effects intrinsic to the exchange bonding type, the same effectsas those of the first embodiment can be obtained. In addition, thefollowing effects intrinsic to the abutted junction type MR head can beobtained.

In this embodiment, since the Co type hard magnetic film 17 has a highresidual magnetization Mr, the film thickness t necessary to obtain(Mr·t) for applying a sufficient bias to the magnetic sensible layer canbe decreased. Thus, an unnecessary hard magnetic bias that weakens theuni-directional anisotropic magnetic field Hua by the anti-ferromagneticfilm can be decreased. Thus, when the film thickness t of the hardmagnetic film is increased with a low residual magnetization Mr, thenoise is effectively erased. In addition to these effects, in thejunction type of the embodiment, since the film thickness of the basemetal is small, a non-magnetic metal film can be prevented from adheringto edge portions of the magnetic sensible layer. Thus, the bias magneticfield can be effectively applied.

In addition, even if the value of (residual magnetization Mr×filmthickness t) is the same in the abutted junction type [or the value of(residual magnetization Mr×hard magnetic film thickness t+saturatedmagnetization of magnetic sensible layer Ms×film thickness of magneticsensible layer t) is the same in the exchange coupling bias type], theprobability of the occurrence of the Barkhausen noise variescorresponding to the residual magnetization Mr. FIG. 31 shows therelation between the probability of the occurrence of the Barkhausennoise and the film thickness of the base metal in the case that thevalue of (Mr·t) is fixed to 3.0 memu/cc. FIG. 32 shows the relationbetween the probability of the occurrence of the Barkhausen noise andthe residual magnetization Mr of the hard magnetic film in the case thatthe value of (Mr·t) is fixed to 3.0 memu/cc. From FIG. 30 and FIG. 31,it is clear that with a hard magnetic film having a high residualmagnetization Mr, a more effectively bias is applied than a hardmagnetic film having a low residual magnetization Mr even if the valueof (Mr·t) is the same. Thus, the Barkhausen noise can be remarkablydecreased.

In the above-described embodiment, a spin valve GMR film was exemplifiedas an MR film. However, the present invention can be applied to amulti-layer film of a ferromagnetic film and a non-magnetic film such asFe/Cr and Co/Cu of which the resistance varies corresponding to theexternal magnetic field (namely, an MR device having an artificiallattice film). In addition, when an AMR film such as NiFe alloy(permalloy) having an anisotropic magnetoresistance effect is used, theabove-described effects can be obtained.

Next, a magnetic record medium according to an embodiment of the presentinvention will be described.

FIG. 33 is a sectional view showing the structure of the magnetic recordmedium according to the embodiment of the present invention. In FIG. 33,reference numeral 41 is a substrate such as a glass substrate, an NiPsubstrate, or an Al substrate. A layer composed of a metal oxide or ametal nitride is disposed as a surface layer 42 on the substrate 41. Thestructural material and so forth of the surface layer 42 are the same asthose of the hard magnetic film structural body according to theabove-described embodiment.

A reactive base film 15 containing a reactive amorphous layer, a crystalmetal base film 16 such as a Cr film, and a Co type hard magnetic film17 are successively formed on the surface layer 42 of the substrate 41.The Co type hard magnetic film 17 functions as a record layer. The filmthickness of the Co type hard magnetic film 17 is preferably 10 nm orless. The reactive base film 15 and the crystal metal base film 16 arefabricated in the same manner as those of the hard magnetic filmstructural body according to the above-described embodiment. The basefilm of the Co type hard magnetic film 17 may be a laminate film of anamorphous layer 19 and a metal crystal layer 20 as with the hardmagnetic film structural body shown in FIG. 2. These films arefabricated in the same conditions and steps of the above-describedembodiment.

For example, a carbon type protection film 43 is formed on the Co typehard magnetic film 17 as a record layer. With these films, a magneticrecord medium 44 is structured.

In the magnetic record medium 44 of the embodiment, since the Co typehard magnetic film 17 as a record layer has a bi-crystal structure, nonoise can be accomplished in high density recording. This is becauseeven if the main-grain is large, the sub-grains of the bi-crystalstructure can function as magnetic grains. In the Co type hard magneticfilm 17 of the embodiment, with a small value of (Mr·t), a good coerciveforce Hc can be obtained. With a small value of (Mr·t), the noise can beremarkably decreased.

In addition, since the sub-grains in the bi-crystal structure have ahigh anisotropic magnetic field Hk, a problem of heat swing in a surfacemagnetic record medium can be properly solved. Moreover, since the Cotype hard magnetic film 17 with the bi-crystal structure has anexcellent surface flatness, it can be suitably applied to a low floatingrecording type and a contact recording type.

To further improve the noise characteristics, the magnetic record mediumof the present invention is suitable to the structure of which the Cotype hard magnetic film 17 as a record layer is separated with anon-magnetic layer. FIG. 34 shows a magnetic record medium with such astructure. A non-magnetic layer 45 composed of a Cr film with a filmthickness of around 3 nm is disposed between a first Co type hardmagnetic film with a film thickness of around 5 nm and a second Co typehard magnetic film 17 b with a film thickness of around 3 nm. Accordingto the present invention, since Co type hard magnetic films 17 a and 17b with a small value of (Mr·t) and a high coercive force Hc areobtained, the structure shown in FIG. 33 can be easily accomplished.

Although the present invention has been shown and described with respectto best mode embodiments thereof, it should be understood by thoseskilled in the art that the foregoing and various other changes,omissions, and additions in the form and detail thereof may be madetherein without departing from the spirit and scope of the presentinvention.

Next, a magnetic storing apparatus such as a magnetoresistance effectrandom access memory (MRAM) to which a magnetoresistance effect deviceaccording to the present invention is applied will be described.

FIG. 35 is a sectional view showing the structure of an MRAM accordingto an embodiment of the present invention. In FIG. 35, reference numeral51 is a substrate such as a glass substrate or an Si substrate. A layercomposed of a metal oxide or a metal nitride is disposed as a surfacelayer 52 on the substrate 51. The structural material and so forth ofthe surface layer 52 are the same as those of the hard magnetic filmstructural body according to the above-described embodiment.

The spin valve GMR film 53 forms on the surface layer 52 of thesubstrate 51. The Co type hard magnetic films 17 are disposed adjacentto the both edges of the spin valve GMR film 53 as a bias magnetic fieldeffect films. The Co type hard magnetic films 17 are formed on thecrystal metal base films 16 composed of Cr film or like. The reactivebase films 15 containing the reactive amorphous layer are disposedbetween the surface layer 52 and the crystal metal base film 16. Thereactive base film 15 and the crystal metal base film 16 are fabricatedin the same manner as those of the hard magnetic film structural bodyaccording to the above-described embodiment. The base film of the Cotype hard magnetic film 17 may be a laminate film of an amorphous layer19 and a metal crystal layer 20 as with the hard magnetic filmstructural body shown in FIG. 2. These films are fabricated in the sameconditions and steps of the above-described embodiment.

A write electrode 55 is disposed on the spin valve GMR film 53 throughan insulation layer 54. A pair of read electrodes 56 are connected atboth edge portions of the spin valve GMR film 53. A sense current issupplied from the pair of read electrodes 56 to the spin valve GMR film53. In FIG. 32, reference numeral 57 is a pair of auxiliary readelectrodes. With these parts, the MRAM 58 is structured.

Information is read and written from/to the MRAM 58 in the followingmanner. When information is written, a current is supplied to the writeelectrode 55 and thereby an external magnetic field is applied in such amanner that the direction of the magnetization of the fixedmagnetization layer of the spin valve GMR film 53 is treated as data “1”or “0”.

When information is read, while a sense current is being supplied fromthe read electrodes 56, a positive/negative pulse current is supplied tothe write electrode 55 and the resultant magnetic field of the currentcauses the direction of the magnetization of the magnetization freelayer of the spin valve GMR film 53 to be reversed.

The direction of the magnetization of the magnetization free layer isnot changed regardless of data “1” or “0” of the magnetization of thefixed magnetization layer. On the other hand, depending on the directionof the magnetization of the fixed magnetization layer stored as data “1”or “0”, when the pulse current of the write electrode 55 is positive,the directions of the magnetization of the upper and lower ferromagneticlayers of the spin valve GMR film 53 are in parallel or not in parallel.Thus, when a pulse current that varies from positive to negative issupplied to the write electrode 55, depending on whether the resistanceof the sense current decreases or increases, data “1” or “0” of thefixed magnetization layer is determined.

The bias magnetic field applying film of the MRAM 58 controls theintensity of the magnetic field of which the magnetization reversal ofthe magnetization free layer takes place when a positive/negative pulsecurrent is supplied to the write electrode 55. Alternatively, the biasmagnetic field applying films suppresses the noise due to irregularmagnetization reversal in the state that a magnetic domain is formed.The bias magnetic field applying film should be a thin filmcorresponding to high integration of the final product and have a biasforce that sufficiently suppresses the increase of theanti-magnetization corresponding to a small cell size. As described inembodiments of the hard magnetic film structural body, with the biasmagnetic field applying films according to the present invention, asufficient bias force can be obtained. Thus, the high integration of theMRAM 58 can be accomplished.

1. A magnetoresistance effect device comprising: a substrate having amain surface; a magnetoresistance effect film formed on the main surfaceof the substrate and having a magnetic field detecting portion; a pairof bias magnetic field applying films, each being disposed adjacent toboth edge portions of the magnetoresistance effect film, said each ofthe bias magnetic field applying films comprising a hard magnetic filmcontaining Co as a structural element; and an under-layer having athickness of 5 to 50 nm disposed between the substrate and the hardmagnetic film, the under-layer being composed of an amorphous layerformed on the main surface of the substrate and a metal crystal layerformed between the amorphous layer and the hard magnetic film.
 2. Themagnetoresistance effect device as set forth in claim 1, wherein saidhard magnetic film containing Co as a structural element has Co(110)oriented perpendicular to the surface thereof.
 3. The magnetoresistanceeffect device as set forth in claim 1, wherein said pair of biasmagnetic field applying films are abutted against said magnetoresistanceeffect film.
 4. The magnetoresistance effect device as set forth inclaim 1, wherein said hard magnetic film is composed of CoPt alloy. 5.The magnetoresistance effect device as set forth in claim 1, wherein thehard magnetic film has a residual magnetization Mr of 650 emu/cc ormore.
 6. The magnetoresistance effect device as set forth in claim 1,wherein the magnetoresistance effect film is a spin valve filmcomprising a ferromagnetic film and a non-magnetic film.
 7. Themagnetoresistance effect device as set forth in claim 1, wherein thehard magnetic film has a bi-crystal structure.
 8. The magnetoresistanceeffect device as set forth in claim 1, wherein the metal crystal layeris formed of a crystal metal material having a bcc structure, thecrystal metal material being at least one selected from the groupconsisting of Cr, V, and an alloy thereof.
 9. A magnetic head,comprising: a lower magnetic shield layer; a magnetoresistance effectdevice formed on said lower magnetic shield layer through a lowerreproduction magnetic gap, said magnetoresistance effect device being asset forth in claim 1; and an upper magnetic shield layer formed on saidmagnetoresistance effect device through an upper reproduction magneticgap.
 10. A magnetic recording/reproducing head, comprising: areproducing head having a magnetic head as set forth in claim 9; arecording head having a lower record magnetic pole in common with saidupper magnetic shield layer of said magnetic head, a record magnetic gapformed on the lower record magnetic pole, an upper record magnetic poleformed on the record magnetic gap, and a record coil for supplying arecord magnetic field to the lower record magnetic pole and the upperrecord magnetic pole.
 11. The magnetoresistance effect device as setforth in claim 1, wherein the metal crystal layer comprises crystalgrains, the crystal grains having an average diameter of five times ormore of a thickness of the metal crystal layer.
 12. Themagnetoresistance effect device as set forth in claim 1, wherein themetal crystal layer constitutes a non-ferromagnetic metal material.